Polythioether polyurethanes and their preparation

ABSTRACT

Novel polythioether polyurethanes of superior thermal and oxidative aging stability are prepared from polythioether dithiols derived from addition of dithiols to acetylenes under free radical conditions. These polythioether dithiols having alkyl branching contain the divalent alkylene groups derived from their dithiol and acetylene monomer components in a regularly alternating manner. This dithiol is reacted with an epoxide with an amine catalyst to form a polythioether diol of the formula ##STR1## wherein R is a C 1  -C 30  divalent organic radical, R&#39; is selected from the group consisting of H, C 1  -C 30  alkyl, C 2  -C 30  alkenyl, C 2  -C 30  alkynyl, C 7  -C 20  aralkyl and mixtures thereof, provided that either R has a branched structure or R&#39; is alkyl, R&#34; is H or methyl and n is 2 to 1000. These polythioether diols are chain extended and crosslinked via reactions with organic diisocyanates of the formula R&#39;&#34; (NCO) 2  to yield polythioether polyurethanes of the repeating structure: ##STR2## wherein R, R&#39;, R&#34; and n are as defined above and R&#34;&#39; is phenylene, tolylene, xylylene, diphenylmethane, chlorophenylene and C 2  to C 12  polymethylene. These polythioether polyurethanes possess superior thermal and oxidative aging stability.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Rule 60 Division of Ser. No. 516,088 filed Oct.18, 1974, now U.S. Pat. No. 3,954,723, which is a continuation-in-partof Ser. No. 326,108 filed Jan. 23, 1973 now abandoned, Oct. 18, 1974,which is a division of Ser. No. 47,109, now U.S. Pat. No. 3,717,618,which in turn is a continuation-in-part of Ser. No. 541,696, filed Apr.11, 1966, now U.S. Pat. No. 3,592,798.

BACKGROUND OF THE INVENTION

Polythioethers of high molecular weight are a widely investigated usefulclass of polymers. Most high molecular weight polythioethers have beenprepared by the anionic polymerization of episulfides. With theexception of the highly crystalline polyethylene-sulfide, these polymersare useful as elastomers. These elastomers are generally copolymers.Minor amounts of olefinic unsaturation are incorporated into the polymerchain as crosslinking sites. This unsaturation is derived from anunsaturated episulfide comonomer.

The successful crosslinking of high molecular weight unsaturatedepisulfide copolymers initiated further research to find novel types ofreactive polythioethers which can be crosslinked to rubbery networks.Such rubbers are of high interest mainly because their high sulfurcontent results in very good hydrocarbon solvent resistance andexcellent aging characteristics.

The preparation of some terminally difunctional polythioethers by theaddition of dithiols to diolefinic hydrocarbons has been known for sometime. For example, Marvel and Chambers, J. Am. Chem. Soc. 70, 999 (1948)and Marvel and Cripps, J. Polymer Sci. 8, 313 (1952) reported thereaction of dithiols with conjugated dienes such as butadiene and withdienes having isolated double bonds. However, such reactions proceededat very slow rates and often resulted in unsaturated thioethers.

Numerous polythioethers were prepared by the ring opening ofepisulfides. The terminal groups of these polymers were generally notdisclosed. However, they can be inferred on the basis of the initiatorsused since the mechanism of such ring opening reactions is known. It canbe safely assumed that these polythioether preparations did not resultin diterminally thiol and/or vinyl sulfide functional polymers. Inherentto the episulfide ring opening catalysts used, generally polythioetherscontaining only one thiol group were formed. The other end group derivedfrom the initiator was usually a nonreactive hydrocarbon end group. Forexample, Boileau produced naphthyl terminated polythioether thiols byusing sodium naphthyl as an initiator as described in the journal Compt.rend. (Paris) 254, 2774 (1962). Another example is given by the ethylterminated polythioether thiol polymers which were produced by zincdiethyl initiator as disclosed in U.S. Pat. No. 3,222,326, incorporatedherein by reference.

The use of amines as initiators of episulfide polymerization resulted inpolyfunctional polythioethers. However, their use also resulted in theincorporation of nitrogen into the polymer (see, for example, U.S. Pat.No. 3,325,456).

Some polythioethers having reactive thiol end groups are disclosed inU.S. Pat. No. 3,337,487, incorporated herein by reference. Thesepolythioethers result from the cleavage of nonfunctional very highmolecular weight polymers derived by episulfide polymerization. Sinceepisulfides such as ethylene and propylene episulfide cannot becopolymerized in an alternating manner, the method disclosed results inthiol terminated copolymers having a random structure.

PRIOR ART VERSUS THE PRESENT INVENTION

Polyethylene thioethers terminated by hydroxyl groups were described inU.S. Pat. No. 2,916,519 by C. Wegner et al., as being derived, e.g. fromthiodiglycol, ethylene oxide, hydrogen sulfide and carbon disulfide.##STR3## These polymers in contrast to those of the present invention,have a high tendency to crystallize with increasing molecular weight. Assuch, they cannot be used as liquid prepolymers at room temperature.

In general, the previously known hydroxyl terminated polythioethers hadnonbranched linear structures having a high crystallization tendency. Incontrast, the present polythioether diols have pendant alkyl groupswhich inhibit their crystallization.

Nonbranched hydroxyl terminated polymers were also prepared via thedehydration of, e.g. thiodiglycol, as it is described in U.S. Pat. No.3,027,354 by H. Holtschmidt and E. Mueller: ##STR4## These prepolymerswhich contain oxy as well as thioether groups, were reacted withdiisocyanates to produce polyurethane elastomers, as is also describedin the same patent. The branched polythioethers of the present inventionundergo a similar polyurethane formation when reacted withdiisocyanates. However, the novel polyurethanes formed are free from theoxidative aging problems of polyurethanes containing oxyether groups.

Polythioether dithiols can be also reacted with diisocyanates to formpolythiourethanes. These polymers, however, have a reduced thermalstability, due to the presence of the labile ##STR5## linkage. Incontrast, the polyurethane derivatives of the present hydroxyl cappedpolythioethers are thermally stable because chain extension occurred viathe formation of the stable ##STR6## linkage.

SUMMARY OF THE INVENTION

Polythioethers, useful in the practice of this invention, are preparedby reacting an acetylenic compound with a dithiol. The polymers soformed are liquid or crystalline depending on the structure of thedithiol and acetylenic compound.

The polythioethers of this invention have the general formula: ##STR7##wherein R is a C₂ -C₃₀ divalent organic radical; R' is H or a C₁ -C₃₀hydrocarbyl radical, providing that either R has a branched structure orR' is alkyl; T and U are independently selected from the groupconsisting of H, --CH═CHR' and mixtures thereof and n varies from 1 to1000.

The preferred terminally difunctional products of this invention areessentially colorless liquids or low melting solids having a numberaverage molecular weight of about 200 to 200,000. They are readilycrosslinked and chain extended by conventional methods.

Polymers of diterminal thiol functionality were found especiallyattractive for crosslinking. They could be converted by monoepoxidesunder anionic conditions via a surprisingly selective reaction to thecorresponding polythioether diols as shown by the following scheme:##STR8## wherein R" is hydrogen, methyl, preferably hydrogen.

The polythioether diols in turn can be chain extended and crosslinked asindicated: ##STR9## wherein R'" is phenylene, tolylene, xylylene,diphenylmethane, chlorophenylene, C₂ to C₁₆ polymethylene, such ashexamethylene, including polymethylene groups interrupted by thioethersulfur.

The crosslinked products are elastomers or resilient plastics havingoutstanding aging properties and solvent resistance.

DETAILED DESCRIPTION Derivation of the Polymer Backbone

A method for preparing polythioethers having thiol or vinylic terminalfunctionality is described in copending U.S. application Ser. No.541,696, now U.S. Pat. No. 3,592,798, incorporated herein by reference.The process involves the free radical addition of dithiols to acetyleniccompounds. The structure of the resulting polythioether is dependent onthe structure of the thiol and acetylenic compounds from which they arederived. Due to the nature of the reaction mechanism, the compounds soformed have incorporated therein the divalent carbon moiety derived fromthe acetylenic compound and the divalent alkylene bis-thio radicalderived from the dithiol in a regular alternating manner.

Hence, the products of the reaction have a repeating structure which isbroadly described by repeating unit of the general formula: ##STR10##wherein the --S--R--S-- fragment represents the residue derived from thethiol monomer and the ##STR11## fragment is the residue of theacetylenic compound from which the polymer is prepared.

The dithiols suitable for use in the preparation of the intermediates ofthis invention have the general formula: HSRSH wherein R is a divalentorganic radical. Preferably, R is a C₂ -C₃₀ divalent organic radical.

The organic radical may have incorporated into its structure sulfur,oxygen or silicon in addition to carbon and hydrogen. The sulfur andoxygen containing organic radicals may contain thioether, ketone andcarboxylic ester groups, but no oxyether group.

Both sulfur and oxygen in either of its forms may be present in the sameorganic radical.

In its preferred embodiment, the dithiol is a dithiol wherein R is a C₂to C₃₀ divalent hydrocarbon radical. The divalent radical may be asaturated radical, e.g. alkylene, an unsaturated radical, e.g. acyclicor alicyclic alkenes or alkynes, a bis-alkylene substituted aromaticradical or an aromatic radical, e.g. m-phenylene.

The divalent alkylene radicals are preferably C₂ -C₁₈ alkylene radicals,more preferably C₂ -C₁₂ alkylene, most preferably C₂ -C₄ alkylene, e.g.trimethylene. Illustrative examples of dithiols wherein R is a divalentalkylene radical are: decane dithiol, ethane dithiol, propane dithiol,butanedithiol, pentanedithiol, hexanedithiol, dodecane dithiol,docosanedithiol, triacontanedithiol, cyclohexane dithiol,cyclododecanedithiol, cyclohexane bis(ethanethiol),2,2-dimethyl-1,3-propanedithiol, etc.

The acyclic or alicyclic alkene dithiols or alkyne dithiols suitable foruse in the practice of this invention are internally unsaturateddithiols, preferably C₄ -C₁₂ alkenedithiols, more preferably C₄ -C₈alkenedithiols. Illustrative examples of dithiols wherein R is anunsaturated divalent radical are 2-butene-1,4-dithiol,3-hexene-1,6-dithiol, cyclohexene dithiol, 4-octene-1,8-dithiol,2-butyne-1,4-dithiol, cyclododecene dithiol, 6-docosene-1,12-dithiol and10-triacontene-1,30-dithiol.

Although the saturated and unsaturated thiols listed above areessentially terminally difunctional thiols, secondary dithiols are alsosuitable for use in the preparation of intermediates for the practice ofthis invention.

The aromatic compounds suitable for use as dithiol reactants arepreferably C₆ to C₃₀ aromatic compounds; preferably these aromaticcompounds contain about 6 to 10 carbon atoms, e.g. 8 carbon atoms.Illustrative examples of these aromatic compounds are m-phenylenedithiol, 1,5-naphthylene dithiol, biphenylene dithiol, terphenylenedithiol, quadriphenylene dithiol, xylene dithiol, durene dithiol andt-butylbenzene dithiol.

The C₂ -C₃₀ divalent organic radicals containing sulfur, oxygen orsilicon preferably contain 2 to 12 carbon atoms, more preferably about 4to 10 carbon atoms, most preferably about 4 to 6 carbon atoms.Illustrative examples of such organic dithiols suitable for use in thepractice of this invention are thio-bis-ethanethiol,thio-bis-benzene-thiol, ethylene-bis-carboxyethanethiol,3-hydroxy-propanedithiol, terephthaloyl-bis(methanethiol),dimethylsylyl-bis(ethanethiol) and diphenylsylyl-bis(ethanethiol).

Particularly preferred thiols are those compounds wherein R is a C₂ -C₄alkylene radical since such intermediates are especially reactive andyield polymers of outstanding resistance to autoxidation and hydrocarbonsolvents.

The acetylenic compounds useful as starting materials have the generalformula:

    CH.tbd.CR'

wherein R' is a hydrogen radical or a C₁ -C₃₀ hydrocarbon radical.Preferably R' is (1) H; (2) a C₁ -C₃₀ alkyl group, e.g. methyl, ethyl,etc.; (3) a C₂ -C₂₀ alkenyl radical such as vinyl, allyl, etc.; (4) a C₂-C₃₀ alkynyl radical, e.g. ethynyl, and (5) a C₇ -C₂₀ aralkyl radicalsuch as benzyl, phenylethyl, naphthyl, methyl.

Where R' is H, the compound is obviously acetylene. Preferably, R' is ahydrocarbyl radical.

Where the hydrocarbyl radical is an alkyl group, it preferably comprisesa C₁ to C₁₀ alkyl radical; more preferably C₁ -C₆, most preferably C₁-C₄. R' may be cycloalkyl. Illustrative examples of such alkyl radicalsare methyl, propyl, hexyl, octyl, dodecyl, eicosyl, docosyl, triacontyland cyclohexyl.

Where the hydrocarbyl radical is an alkenyl radical, it is preferably aninternally unsaturated C₄ -C₁₀ radical. Illustrative examples of suchalkenyl radicals are 2-butenyl, 3-hexenyl, cyclohexenyl, 4-octenyl,cyclododecenyl, docosenyl, triacontenyl, etc.

The hydrocarbyl alkynyl radicals are preferably internally unsaturatedradicals, more preferably C₄ to C₆ alkynyl radicals such as 3-hexynyland triacontynyl.

Where R' is an aralkyl, it is preferably a C₇ to C₁₀ aralkyl.Illustrative of aralkyl radicals are benzyl, phenylethyl, naphthylmethyl, phenyloctyl and phenyldocosyl.

Preferably, R' is a hydrocarbyl radical of less than 10 carbon atoms.The preferred acetylenic compounds are those compounds in which R' is aC₁ to C₆ hydrocarbyl radical, more preferably, a C₁ -C₄ alkyl radical.The preferred acetylenic compounds are acetylene, methylacetylene,butylacetylene and benzylacetylene.

The reactions by which the products of this invention are prepared arerepresented by the following equations: ##STR12##

The preferred intermediates are essentially colorless liquid or lowmelting solids having a number average molecular weight of about 200 to200,000, preferably about 500 to 20,000. Hence, "n" may vary from about1 to about 1,000, preferably 2 to 1,000, more preferably "n" is about 2to about 100, most preferably 3 to 40. The liquid polythioether productsare particularly preferred in mastics and sealants. Such liquid adductsare essentially castable rubbers.

The liquid state of the polythioethers is strongly dependent on theirstructure. The tendency toward crystallinity is increased through theintroduction of branching, e.g. R' ≠ H and selecting R so that it isbranched and/or greater than a C₂ divalent carbon radical. It is wellknown that increasing the distance between subsequent sulfur atoms in apolythioether reduces crystallinity.

Intermediates and Products

The intermediates of this invention are broadly defined by the generalformula: ##STR13## where R and R' are as previously defined, T and U areindependently selected from the group consisting of H and ##STR14## andn is about 1 to about 1,000. Preferably, R" is H. Where at least onemember of the group T and U is H, R must not be ##STR15## For example,where R" is H and R' is methyl, R may not be ##STR16##

In a more specific embodiment of this invention, R is a divalentalkylene radical of the formula --C_(x) H_(2x) -- and R' is --C_(y)H_(2y+1) -- wherein x is 2 to 30, preferably 2 to 12, more preferably 2to 4, e.g. 3; and y is 0 to 30, preferably 0 to 4. It is obvious thatwhere y is O -- C_(y) H_(2y+1) -- is H, otherwise the formula denotes analkyl radical.

In another specific embodiment, R is more simply --(CH₂)_(x) -- and R'is --(C_(y) H_(2y+1))-- x and y being as previously defined.

The terminally difunctional polythioether compounds of this inventioncan be defined as thiol and/or vinyl sulfide terminated difunctionalpolythioether polyadducts. The preferred products are the dithiolterminated adducts.

The ratio of reactants present in the reaction zone has a strong effectupon the molecular weight of the final product. In general polymershaving a number average molecular weight between 500 and 4000 aresecured when an equal molar ratio of dithiol to acetylenic compound ispresent in the reaction zone. Higher molecular weight thiol terminatedpolythioethers are secured when the molar ratio of thiol compound toacetylenic compound is maintained between about 1:1.01 to 1:1.3.

Although the direct use of low molecular weight polythioether dithiolsfor the preparation of polymer articles is commercially less attractive,they can be advantageously used for the preparation of higher molecularweight polythioetherdithiols by reacting them with further amounts of anacetylene in the next step. For example: ##STR17##

Preferred intermediate compositions include polythioetherdithiols of theformula: ##STR18## wherein R and R' are as previously defined and##STR19##

More preferably such polythioetherdithiols include those of the formula:##STR20## wherein x, y and n are as defined earlier and --C_(x) H_(2x)-- does not equal --CH₂ CH(C_(y) H_(2y+1))--.

Further illustrative examples of polythioetherdithiols of this inventionare: ##STR21## Another specific embodiment of the novel compositionsincludes diterminally functional polythioethers having one thiol andvinyl sulfide end group of the following formula: ##STR22## wherein Rand R' are as previously defined with the limitation that ##STR23##

Chain Extension and Crosslinking

Although the addition products of the present invention have many usesas intermediates because of the thiol or vinyl terminal functionalitypresent on the polymers, they find particular utility as the basesubstituent for mastic compositions. The thiol terminated additionproducts of this invention can be readily crosslinked to stable rubberythree-dimensional networks using a variety of techniques.

For example, the polythioetherdithiol addition products may beoxidatively chain extended by mixing the polymers with from 1 to 20grams per 100 grams of polymer of dimethylsulfoxide and heating thetotal mixture at a temperature varying from 80° to 150° C. for a periodranging from 1 to 5 hours.

In another example, 5 parts of the polythioetherdithiol is mixed with 2parts of a curing composition containing 50% of lead dioxide as anoxidizer, 5% stearic acid as a retarder and 45% dibutyl phthalate as aplasticizer. About 2.5 grams of carbon black of Thermax brand is alsoadded as a filler. Dependent on the thiol functionality curing occurredin about 24 to 36 hours when the mixtures were allowed to stand at roomtemperature in a desiccator containing a saturated solution of aqueoussodium thiocyanate. Other metal peroxides, sulfur and organic peroxidescan be also used for oxidative crosslinking.

For the oxidative crosslinking of polythioetherdithiols tetrathiols isnecessary. The oxidation of dithiols results in chain extension whilethe polythiols contribute to crosslinking as indicated by the followingreaction scheme: ##STR24## Dependent on the amount and functionality ofthe polythiol component vulcanized networks of various crosslinkdensities can be obtained. Suitable polythiols are1,2,3-propanetrithiol, the trithiol adduct of H₂ S andtrivinylcyclohexane, benzenetetrathiol, etc.

As another example of curing methods, polythioetherdithiols are treatedwith epoxides having at least 2 epoxide groups per molecule in thepresence of a base catalyst usually an amine. For example, 1.2 moleequivalent of Epon-830, a bis-phenol-A-diglycydyl ether resin, isreacted with 1.0 mole equivalent of a polythioetherdithiol in thepresence of 5 wt. % DMP-30 amine catalyst, i.e.tri-2,4,6-(dimethylaminomethyl)phenol. Chain extension takes place atroom temperature due to the thiolepoxide reaction. The cure is completedin two hours at 100° due to the reaction of the hydroxy groups formedwith the excess epoxide. The type of reactions involved are indicated bythe following reaction scheme. ##STR25##

Polythioetherdithiols undergo similar amine catalyzed reactions withdiepisulfides. These reactions, however, do not require heating forcomplete cures, since chain extension and crosslinking both occur undermild conditions.

Alternatively, the polythioetherdithiols can be cured with aboutequimolar amounts on an excess of a diisocyanate to producepolythiourethanes.

It was found in the present invention that it is particularlyadvantageous to modify the polythioetherdithiol with an equivalentamount of a monoepoxide at first and then crosslink the resultingpolythioetherdiol with a diisocyanate. As is shown by the reactionscheme, such a reaction produces more stable polyurethanes rather thanthe less stable polythiourethanes.

In the reaction scheme, the formula of the polythioether dithiols isreplaced by the symbol HS SH. It is emphasized that the first reactionwith the ethylene or propylene oxide is selective to produce hydroxylterminated polymers substantially free from oxy-ether groups as shown:##STR26## Such reactions can be also effectively and selectivelycatalyzed by C₁ to C₄ trialkyl amines such as triethylamine,trimethylamine. In the presence of the above catalysts, the opening ofthe epoxide ring by the thiol reactant occurs via an anionic mechanism.Accordingly, the use of a substituted epoxide such as propylene oxideresults in disecondary diol products. Using the above catalysts, theformation of products containing oxy-ether groups is substantiallyavoided. This is due to the sharply reduced rate of the hydroxyl-epoxidereaction of the products compared to that of the thiol-epoxide reactionof the starting reactants.

The selective dithiol monoepoxide reactions are preferably carried outat temperatures between 10° and 100° C, more preferably, between 30° and50° C. The preferred catalyst is triethylamine and the preferred epoxideis propylene oxide. It is preferred that the concentration of the aminebe between 5 and 200, more preferably, 5 and 50 mole percent based onthe dithiol. The amount of the epoxide reactant is preferably between 2and 2.5 moles per dithiol.

The polythioether diol-diisocyanate reactions are carried out in themanner known for polyoxyether diol-diisocyanate reactions. Typicalprocedures are described in the monograph "Polyurethanes" which appearedas Volume XVI of the High Polymers Series. The latter was published bythe Interscience Division of J. Wiley and Sons in New York, 1962.

Polythioetherdithiols can be also chain extended and crosslinked byreacting them with di- and polyolefinic and polyacetylenic unsaturates.It is preferable to use unsaturated compounds having olefinic bondsactivated towards thiol addition. For chain extension diunsaturatedcompounds such as diacrylates, diacrylamides, dipropiolates, diallylmaleate, divinyl sulfone can be advantageously used, e.g. ##STR27## Forcrosslinking, tri- or polyfunctional unsaturated compounds can be used,alone or in addition to a diunsaturate. Examples of the types of suchsuitable crosslinking reagents are triacrylates, triacrylamides,tripropiolates, tetraacrylamides. Crosslinking reactions with thesereagents can be catalyzed with bases such as tertiary amines. such aspolyolefins such as polyethylene, polypropylene, polyvinylchloride,ethylene-propylene copolymer, etc. Such blends can be advantageousbecause of their increased oxidation stability, particularly in thepresence of phenolic inhibitors.

In such blends, the terminally vinyl and/or thiol functionalpolythioether is usually a minor component. It is preferable to use itin amounts less than 25 wt. %, more preferably between 0.05 and 10 wt.%.

Our terminally difunctional polymers can be also blended with asphaltand vulcanized thereafter. In such blends either the asphalt or thepolythioether can be the major component although it is preferred tohave major amounts of the asphalt.

Prior to curing operations, the addition products may be compounded withstabilizers, plasticizers or extender oils, asphalts and various typesof fillers. For example, carbon black, petroleum, coke or mineralfillers may be incorporated into the polymer up to about 10 parts,preferably up to 200 parts, of filler per 100 parts of polymer. Amongthe carbon blacks that may be compounded with the addition productpolymer are the channel blacks such as ETC, MPC, HPC, etc. (theseletters denoting carbon black products well known to the trade), thefurnace blacks including SRF, HAF, etc., and the thermal blacks. Themineral fillers which may be used include any of the usual noncarbonblack fillers or pigments such as the oxides, hydroxides, sulfides,carbonates, and so forth of silicon, aluminum, magnesium, titanium, zincor the like, or the silicates or aluminates of the various elementsabove-indicated.

The cured mastic compositions of this invention are highly resistant toozone and oxygen degradation even at elevated temperatures and arerelatively immune to attack by organic solvents. Hence, the curedmaterials find particular utility in automotive applications and asgasketing materials.

The invention will be further understood by reference to the followingexamples.

EXAMPLE 1

One gram mole (108 grams) of trimethylenedithiol was placed in a quartzpressure tube equipped with a magnetic stirrer. The tube was evacuatedand 40 grams (1 gram mole) of methylacetylene was condensed therein. Thereaction vessel was closed, placed in a water bath maintained at atemperature varying between 15° and 17° C., and the contents irradiatedwith constant stirring with a 70 watt high pressure Hanau immersionlamp. After a reaction period of 11 hours wherein the reactants wereconstantly agitated and subjected to ultraviolet irradiation, thereaction vessel was opened and the addition product recovered. All ofthe volatile starting materials and most of the volatile products wereremoved from the product by bubbling nitrogen for one hour through theproduct contained in a vessel maintained at a temperature of 150° C. and25 millimeters of mercury. Following the distillation procedure, 134grams (94% yield) of a polythioetherdithiol was obtained as clear,colorless, viscous liquid product.

Nuclear magnetic resonance analysis (NMR) of the product showed thepresence of characteristic triplets centered at about 2.64 p.p.m.downfield from tetramethylsilane for the alpha-methylene, SCH₂, group; acharacteristic quintriplet centered at about 1.74 p.p.m. for the middlemethylene, CH₂, group; and a typical doublet at 1.34 p.p.m. for themethyl group. The lack of vinylic proton signals in the NMR spectrumindicated that the polythioether was saturated. The presence of thethiol groups was confirmed by potentiometric titration of the productwith silver nitrate. The average molecular weight of the product asdetermined by low pressure osmometry in benzene solution was 1112.

On the basis of NMR analysis and molecular weight determination, theproduct is believed to have the following structure: ##STR28##

An elemental analysis of the product also supported the assumedstructure. The calculated elemental composition for HS[(CH₂)₃ SCH₂CH(CH₃)S]₆ (CH₂)₃ SH (calculated molecular weight 1146): C, 47.15; H,8.09; S, 44.76. Found: C, 47.70; H, 8.15; S, 44.91.

EXAMPLE 2

Following the procedure of Example 1, one gram mole (94 grams) ofethanedithiol was reacted with 40 grams (1 gram mole) of methylacetylenefor 33.5 hours. After heating the crude product to 175° C. at 0.3millimeters of mercury to remove the volatile reactants and products,129 grams (96% yield) of viscous liquid polymeric product was recovered.The average molecular weight of the polymer as determined by lowtemperature osmometry in benzene solution was found to be 2532. From themolecular weight determination and an NMR structure analysis, theprincipal product was believed to have the following structural formula:##STR29## An elemental analysis of the product also supported theassumed structure. The calculated elemental composition for C₉₂ H₁₈₆ S₃₈(molecular weight 2511; n = 18): C, 44.01; H, 7.46; S, 48.53. Found: C,44.15; H, 7.52; S, 48.73.

EXAMPLE 3

Following the procedure of Example 1, 108 grams (1 gram mole) of1,2-propane dithiol was reacted for 48 hours with 40 grams (1 gram mole)of methylacetylene. Following the reaction, the unreacted reagents andvolatile adducts were removed by a one-hour distillation at 150° C. Thefinal polythioetherdithiol product weighed 126 grams (85% yield). Itsmolecular weight was found to be 1604. The calculated composition forC₆₃ H₁₂₈ S₂₂ (molecular weight 1591): C, 47.56; H, 8.10; S, 44.34.Found: C, 47.36; H, 8.33; S, 43.79.

EXAMPLE 4

One-fifth molar quantities (21.6 grams each) of trimethylenedithiol werereacted with varying amounts of methylacetylene starting with an equalmolar amount (8 grams) and with amounts in excess of equal molarquantities up to reactions where 100 mole % excess of methylacetylenewas used. The reaction was conducted according to the proceduredescribed in Example 1. The viscosities of the reacting mixturesincreased with increasing excess of methylacetylene indicating thedirect effect of the latter on the molecular weights of thepolythioethers formed.

Molecular weight determinations of the various products indicated thatan excess of 20 mole % of methylacetylene resulted in a product having anumber average molecular weight of 4742. Products obtained whenmethylacetylene was present at 50 mole % and 100 mole % excess exhibitednumber average molecular weight of 4286 and 2532, respectively.

EXAMPLE 5

Three-tenths of a mole of trimethylenedithiol (32.4 grams) was reactedfor 24 hours with a ten-fold molar excess of methylacetylene (120 grams,3 gram moles) according to the procedure of Example 1. The resultingproduct was heated to 210° C. at 0.35 millimeters of mercury in adistillation apparatus to remove volatile materials. The residualproduct (30 grams, 86% yield) had a molecular weight of 842 asdetermined by low pressure osmometry. The NMR spectrum of the productshowed that it had propenyl end groups as shown in the assumed productstructure below. ##STR30## An NMR analysis of the distillate by-product(5 grams) showed that it consisted of a mixture of the following twomonoadducts: ##STR31##

EXAMPLE 6

Into a quartz tube containing 94 grams (1 gram mole) of ethanedithiolwas bubbled gaseous acetylene. The reactants were subjected toultraviolet light irradiation and maintained at a temperature of 17° C.Acetylene addition was continued for five days. The resulting productwas then heated to 115° C. at 0.3 millimeters of mercury pressure toremove unreacted dithiol. The residual product, weighing 20.5 grams wasbelieved to be a diadduct of acetylene and ethanedithiol having theassumed structure:

    HS(CH.sub.2).sub.2 S(CH.sub.2).sub.2 S(CH.sub.2).sub.2 SH

the structure of the above product was confirmed by NMR analysis andthiol end group titration.

EXAMPLE 7

A mixture of 86.4 g. (0.20m) of trimethylenedithiol and 35 g. (0.875m)of methylacetylene contained in a Pyrex pressure tube was irradiated inan aluminum vessel from 7.5 cm distance by a Co⁶⁰ source emittinggamma-rays of about 6000 Curie intensity for 30 minutes. The tube wasopened and evacuated to a pressure of 30 mm of mercury to remove theunreacted methyl acetylene. The crude product was then heated at 135° C.under 0.5 mm of mercury pressure to remove all the volatile components.This resulted in the recovery of 107 g. (about 90% yield) of thepolyadduct in the form of a colorless, viscous liquid polymer. An NMRspectrum of the product indicated that it was virtually free fromvinylic unsaturation. The product exhibited a number average molecularweight as determined by the osmotic method of 4330.

EXAMPLE 8

A mixture of 64.8 g. (0.6 m) of trimethylenedithiol and 48 g. (1.2m) ofmethylacetylene contained in a Pyrex pressure tube was irradiated as inthe previous example with Co⁶⁰ plates for 30 minutes. Most of the excessmethylacetylene was released on opening the reaction tube. The remainingunreacted material was removed on evacuation to 20 mm of mercury leaving92.5 g. of residual product. On heating this product at 135° - 138° C.under 0.15 mm of mercury pressure, 5.8 g. of a distillate was obtained.The residue consisted of 85 g. of a colorless somewhat viscous liquid.Its NMR spectrum showed the presence of vinylic unsaturation. Itsaverage molecular weight as determined with the osmosis method was 1170.

EXAMPLE 9

A solution of 54 g. (0.5 m) of trimethylenedithiol and 20.3 g. (0.5075m) of methylacetylene in 53 g. methyl sulfide contained in a quartzpressure tube was irradiated by ultraviolet light at 16° C. for 3.5hours. The solvent was then removed at 30 mm of mercury pressure at roomtemperature. The remaining crude product (69 g.) was heated between130° - 140° C. for 2 hours to remove the volatiles. The residual product(63 g.) was a colorless liquid of moderate viscosity having a numberaverage molecular weight of 876.

EXAMPLE 10

A mixture of 54 g. (0.5 m) of trimethylenedithiol and 29.7 g. (0.55m) ofethylacetylene was irradiated at 16° C. with an ultraviolet lamp in theusual manner for 18 hours. The tube was opened and evacuated to apressure of 30 mm of mercury resulting in the loss of 1.7 g. ofunreacted ethylacetylene. The remaining crude product was heated at 140°C. under 0.2 mm for 2 hours to remove all the volatiles. The residualproduct obtained consisted of 73 g. (91%) of a colorless, viscousliquid. An NMR spectrum of the product indicated no vinylicunsaturation. An osmotic molecular weight determination of the productgave a value of 3943. The calculated molecular weight of the expectedpolythioetherdithiol having a degree of polymerization n, of 23 is 3916.Calculated elemental composition for C₁₆₇ H₃₃₆ S₄₉ (n = 23): C, 51.23;H, 8.64; S, 40.13. Found: C, 51.58; H, 8.50; S, 40.03.

EXAMPLE 11

A solution of 27 g. (1.6 m) of xylylene dimercaptan and 8.6 g. (0.215 m)of methylacetylene in 85 g. methyl sulfide, contained in a quartzpressure tube, was irradiated for 3.5 hours at 16° C. with ultravioletlight. The mixture was then washed with a 5% aqueous sodium hydroxidesolution to remove the unreacted dimercaptan. The methyl sulfide phasewas concentrated by distillation in vacuo and heated at 140° C. under0.5 mm of mercury pressure. The residual polyadduct consisted of 5 g. ofa viscous yellow-orange liquid. Its NMR spectrum showed a polyadductbackbone with no unsaturation. This suggested the expectedpolythioetherdithiol structure. The osmotic molecular weight of theproduct was found to be 875.

EXAMPLE 12

To a stirred melt. mixture of 34 g. (0.2 m) of p-xylylene dimercaptanand 8.2 g. (0.1 m) of 1-hexyne, 0.75 g. (0.0048 m) ofazo-bis-isobutyronitrile was added at 70° C. The mixture was heated to80° C. where an exothermic reaction was observed. After keeping themixture at 80° C. for 6 hours, a sample of the resulting crude productwas examined by NMR spectral analysis. The spectrum failed to show anyunreacted hexyne nor any vinylic monoadduct intermediate present. Theposition and intensity of the observed NMR peaks agreed with thoseexpected for the adduct having the structural formula: ##STR32##

EXAMPLE 13

A mixture of 2.84 g. (0.02 m) of m-benzenedithiol and 1.64 g. (0.02 m)of hexyne was irradiated with ultraviolet light at 16° C. for 2.4 hours.The reaction mixture was sampled periodically for study by NMR. Thehydrogen distribution of the samples indicated that 66% of the freethiol hydrogens disappeared during the first half hour of reaction.After 24 hours, the conversion was 80% on the basis of thioldisappearance. An NMR spectrum also showed 2 vinylic protons for everythiol proton remaining. The rest of the spectrum supported the followingassumed structure: ##STR33## The calculated molecular weight for theabove formula is 1122. The osmotic molecular weight determination gave avalue of 1034. Calculated elemental composition for C₆₀ H₈₀ S₁₀ (n = 4):C, 64.24; H, 7.18; S, 25.58. Found: C, 64.36; H, 7.22; S, 28.94.

EXAMPLE 14

A stirred mixture of 30.5 g. (0.25 m) of tetramethylene dithiol and 14.2g. (0.275 m) of 2-butyne was irradiated with ultraviolet light at 16° C.for 24 hours. The unconverted reactants and all other volatiles werethen removed by distillation. After heating the residual product at 135°C. under 0.1 mm pressure for 2.5 hours, 31.5 g. (71.5% yield) ofslightly yellow, somewhat viscous, clear liquid polymer was obtained.NMR supported the assumed structure of the polymer repeating unit andshowed no vinylic unsaturation. A molecular weight determination byosmometry gave a value of 777. The calculated molecular weight of theassumed polythioetherdithiol product having 4 repeating units is 758.All the data together indicated that on the average, the followingreaction took place: ##STR34##

Calculated elemental composition for C₃₁ H₆₄ S₁₀ (n = 4): C, 49.16; H,8.51; S, 42.33. Found: C, 48.97; H, 8.38; S, 42.74.

EXAMPLE 15

A mixture of 54 g. (0.5m) of trimethylenedithiol and 28.5 g. (0.525m)2-butyne was allowed to stand at room temperature in a quartz pressuretube without any added catalyst. In a few minutes, the temperature ofthe mixture started to rise and in 10 minutes rose to about 60° C. Themixture then slowly came to ambient temperature and was left to standfor 160 hours. Subsequently, the unreacted starting materials and allother volatile compounds were removed. After 21/2 hours at 135° C.,under 0.2 mm mercury pressure, 57 g. (70%) of the residual polymer wasobtained a clear, colorless, slightly viscous, liquid. An NMR spectrumof the polymer indicated the expected polythioetherdithiol structure.The molecular weight by the osmotic method was found to be 653. Thecalculated molecular weight for the assumed polythioetherdithiols havingan average of 3 and 4 repeating units is 595 and 757, respectively.Consequently, our product can be best described by the followingformula: ##STR35##

Calculated elemental composition for the polymer having n = 3, i.e. asummary formula C₂₄ H₅₀ S₈ : C, 48.44; H, 8.46; S, 43.10. Calculatedcomposition for the polymer having n = 1, i.e. C₃₁ H₆₄ S₁₀ : C, 49.16;H, 8.51; S, 42.33. Found composition: C, 48.97; H, 8.38; S, 42.74. Thesedata show that the average number of units, i.e., n for our product isbetween 3 and 4.

EXAMPLE 16

A polythioether dithiol of 1388 average molecular weight derived fromtrimethylene dithiol and methyl acetylene as described in Example 1 wasused for the selective synthesis of the corresponding hydroxyethylatedpolythioethers via reaction with ethylene oxide.

Into 69.4 g (0.05 mole) of the stirred, previously nitrogenated liquidpolythioether dithiol intermediate, 2.6 g (0.05 mole) gaseous trimethylamine catalyst was bubbled. Into the resulting mixture, 4.5 g (0.1 mole)gaseous ethylene oxide was introduced. The resulting reaction mixturewas allowed to stand at ambient temperature for five days to completethe reaction. The trimethyl amine catalyst was subsequently removed inhigh vacuo to leave a colorless liquid residual polythioether diolproduct of the formula ##STR36## as indicated by NMR spectroscopy.

EXAMPLE 17

For a better characterization of polythioether dithiolepoxide reactions,a simple dithiol, ethane dithiol, was reacted with propylene oxide inthe presence of triethylamine. As a result, low molecular weightproducts were obtained via the following anionic ring opening reactions:##STR37## The products of these reactions could be readily analyzed bygas liquid chromatography (glc) and separated by fractional distillationin vacuo. Their structure could then be determined by NMR.

A series of experiments was run using 2.4 moles of the epoxide per moledithiol on the 0.1 to 0.6 g mole dithiol scale. The catalyst wastriethyl amine, usually 0.2 mole per mole dithiol. The epoxide wasusually added dropwise to a stirred, ice-cooled mixture of the dithioland the catalyst. Rapid exothermic reaction occurred after an inductionperiod of several hours at room temperature. If the temperature runs outof control higher molecular weight oligomeric adduct by-products arealso formed. Keeping the reaction temperature below 40° resulted in anessentially complete selectivity to the diadduct.

Equimolar amounts of the reactants provided both the mono and thediadducts.

In a large scale experiment, 561 g (6 mole) of ethane dithiol wasreacted with 697 g (1.2 mole) of propylene oxide in the presence of 121g (1.2 mole) triethyl amine at 40° to yield a crude diadduct of 90%purity according to glc.

On distillation of the crude product, 1107 g (88%) of the colorlessliquid diadduct was obtained between 124°-130° at 0.1 mm. NMR analysisof the product indicated the formation of a bis-secondary diol of thestructure [CH₂ SCH₂ CH(CH₃)OH]₂.

Anal. Calcd. for C₈ H₁₈ O₂ S₂ : C, 45.68; H, 8.62; S, 30.49. Found: C,45.80; H, 8.44; S, 30.72.

EXAMPLE 18

For a further characterization of the polythioether dithiol-epoxidereactions, trimethylene dithiol was reacted with ethylene oxide in thepresence of triethyl amine.

A mixture of 27 g (0.25 mole) of 1,3-propanedithiol and 5.2 g (0.05mole) of triethylamine was placed in a Pyrex pressure tube, equippedwith a magnetic stirrer and a Teflon valve. Then, 32.5 g (0.74 mole) ofethylene oxide was condensed to the evacuated mixture at -70° C. Thestirred reaction mixture was allowed to warm up in an ice bath and thenkept in a room temperature bath overnight. Thereafter, the unreactedvolatile epoxide was removed at 30 mm. A subsequent analysis of thereaction mixture by glc indicated that it contained the dithiol, themonoadduct and the diadduct in a 16:46:17 weight ratio.

What is claimed is:
 1. Process for the preparation of polythioetherpolyurethanes comprising reacting a polythioether diol of the formula##STR38## wherein R" is hydrogen or methyl, R is a C₁ to C₃₀ divalentorganic radical; R' is selected from the group consisting of H, C₁ -C₃₀alkyl, C₂ -C₃₀ alkenyl, C₂ -C₃₀ alkynyl, C₇ -C₂₀ aralkyl and mixturesthereof, providing that either R has a branched structure or R' is alkyland n is 2 to 1000, with a diisocyanate of the formula

    R'"(NCO).sub.2

wherein R'" is phenylene, tolylene, xylylene, diphenylmethane,chlorophenylene, C₂ to C₁₆ polymethylene and polymethylene groupsinterrupted by thioether sulfur, to yield a product of the repeatingstructure ##STR39##
 2. The process of claim 1 wherein R'" ishexamethylene.
 3. The process of claim 1 wherein R" is hydrogen.
 4. Theprocess of claim 1 wherein R" is methyl.
 5. Polythioether polyurethanepolymers of the repeating structure: ##STR40## and their derivativescrosslinked via diisocyanate reactions, wherein R" is hydrogen ormethyl, R is a C₁ to C₃₀ divalent organic radical, R' is selected fromthe group consisting of H, C₁ -C₃₀ alkyl, C₂ -C₃₀ alkenyl, C₂ -C₃₀alkynyl, C₇ -C₂₀ aralkyl and mixtures thereof, providing that either Rhas a branched structure or R' is alkyl and n is 2 to 1000, and R'" isphenylene, tolylene, xylylene, diphenylmethane, chlorophenylene, C₂ toC₁₆ polymethylene and polymethylene groups interrupted by thioethersulfur.
 6. The product of claim 5 wherein R'" is hexamethylene.
 7. Theproduct of claim 5 wherein R" is hydrogen.
 8. The product of claim 5wherein R" is methyl.